Passive Monitor Controller Help

[Strawtles]

Hi. I want to build a relatively simple passive monitor controller with a switch to select three balanced inputs, a 4 gang attenuator and another switch to select three balanced outputs.

My doubt is how to split the balanced signal before the attenuator to send it to the headphone amplifier (with unbalanced inputs)

Is it better to use two transformers or an active circuit?

Below a sketch of the block diagram

 

[abbey road d enfer]

Hi. I want to build a relatively simple passive monitor controller with a switch to select three balanced inputs, a 4 gang attenuator and another switch to select three balanced outputs.

My doubt is how to split the balanced signal before the attenuator to send it to the headphone amplifier (with unbalanced inputs)

Is it better to use two transformers or an active circuit?

Below a sketch of the block diagram

I don't like the idea of introducing a non-linear element (the transformer) in a medium-high impedance circuit. A decent active stage would be perfectly linear.

 

[Strawtles]

Thank you
I was thinking of a circuit like this one

 

[abbey road d enfer]

Thank you
I was thinking of a circuit like this one

It's a good circuit.
Do you know you can increase the resistor values by a tenfold with (almost) no prejudice on noise and reduce loading of the circuit it's eavesdropping?
The opamp should be a FET type for that. A better choice is the OPA2134.
However I would add small caps (about 10pF) between output and inverting input of each opamp, for stability.

 

[Strawtles]

I was was just thinking tu put the OPA2134
Thanks for the tips!

Another thing. Eventually I want to double the unbalanced output, do you think it is enough a simple 100 Ohm resistor, a transformer or another opamp connected to the first output?

 

[abbey road d enfer]

I was was just thinking tu put the OPA2134
Thanks for the tips!

Another thing. Eventually I want to double the unbalanced output, do you think it is enough a simple 100 Ohm resistor, a transformer or another opamp connected to the first output?

Actually it depends what you want to connect to these outputs. A 100r resitor should be OK if there is no ground loop issue. In case of ground loop problems you need either floating outputs (transformer or CCOS) or remote ground-sensing outputs. This subject has been recently discussed.

 

[Strawtles]

Thank you again!